Semiconductor processing involves a number of different chemical and physical processes wherein minute integrated circuits are created on a substrate. Layers of materials which make up the integrated circuit are created by chemical vapor deposition, physical vapor deposition, epitaxial growth, and the like. Some of the layers of material are patterned using photoresist masks and wet or dry etching techniques. The substrate utilized to form integrated circuits may be silicon, gallium arsenide, indium phosphide, glass, or any other appropriate materials.
A typical semiconductor processing chamber may have many components. Some components include a chamber body defining a process zone, a gas distribution assembly adapted to supply a process gas from a gas supply into the process zone, a gas energizer, e.g., a plasma generator, utilized to energize the process gas within the process zone, a substrate support assembly, and a gas exhaust. Some components may be comprised of an assembly of parts. For example, a showerhead assembly may include a conductive base plate bonded to a ceramic gas distribution plate.
Prior showerheads have issues of plasma ignition in the gap between the gas distribution plate and the base plate when exposed to high RF electric field conditions. The plasma may ignite thus causing discolorations of the gas distribution plate and the base plate. Plasma ignitions have generally occurred when higher powers are sought, such as above 2000 watts. The discharged process gases cause polymer deposition on the exposed surfaces of the gas distribution plate and the base plate. The corrosive radicals not only attack the gasket seals or the bonding material of the showerhead assembly, thus resulting in bond seal erosion and/or gasket seal erosion and the loosening of thermal contact, but also attack the anodized base plate and other such protective coatings. The accumulated polymers, loosened bond filler, and/or particles of anodized material may pass through the gas holes of the gas distribution plate and into the plasma chamber, thus causing particle issues and contamination.
Therefore, what is needed in the art is an improved showerhead assembly to reduce backside plasma ignition.